1. Field of the Invention
This invention relates to the field of data processing systems. More particularly, this invention relates to data processing systems including a plurality of trace data sources operable to generate individual trace data streams for diagnostic purposes.
2. Description of the Prior Art
It is known to provide data processing systems with trace data generating mechanisms. Examples of such systems are the Embedded Trace Macrocells designed by ARM Limited of Cambridge, England. Such trace mechanisms serve to monitor the data processing operations taking place and to generate a trace data stream indicative of the data processing operations occurring, such as which instructions are being executed, which data values are being manipulated. This trace data stream is then output (possibly after on-chip buffering) to a diagnostic tool to assist a designer/programmer in debugging the system.
As data processing systems increase in complexity it is becoming common to use system-on-chip designs which typically contain many different data processing elements each performing its own data processing operations and communication with the other data processing elements. As an example, a single integrated circuit may include a processor core, a digital signal processor and a memory system. Each of these elements can be separately subject to tracing and generate its own trace data stream. A problem with providing separate trace mechanisms for each trace data source is that separate inputs and outputs need to be provided for each trace data source in a manner that disadvantageously consumes pin count. Furthermore, the different trace data output formats of some protocols that are appropriate and/or necessary for some data processing elements can present difficulty in a combined data stream.
It is known to provide trace systems which include trace source identifiers within the trace data protocol. These systems include the trace source identifiers with each trace data packet assembled and output.